Synchronous-type circuit interrupter with synchronous-operating holding magnet for latching interrupter in closed position



Nov. 2, 1965 F. KESSELRING ET 3 215 SYNCHRONOUS-TYPE CIRCUIT INTERRUPTER WITH S YNCHRONOUS OPERATING HDLDING MAGNET FOR LATCHING INTERRUPTER IN CLOSED POSITION Filed April 30, 1963 L A A A VV 5i l5 3lu i OP ni E M I 43 IS F 37 4 I I9 MAGNETIC MATERIAL -2 F ig.3. 7

ASYMMETRICAL 4 CURRENT 2 Fig.2.

I SYMMETRICAL Fl 9- CURRENT O l l I t 20 40 so so I WITNESSES (KA) F t INXENTOIR'S fl Z esse l'lfl W M g and Bruno Leisi BY MM M ATTORNEY United States Patent 3 Claims. (a. 200-98) This invention relates generally to synchronous-type circuit interrupters having synchronous-operating holding magnet structures, and, more particularly, to improved and highly effective operating and control arrangements for such synchronous-type circuit interrupters.

A general object of the present invention is to provide an improved and highly eflicient synchronous-type circuit interrupter latched in the closed position and released by a synchronous-operating holding magnet, in which the separable contacts are opened on the descending portion of the alternating current wave, say, for example, approximately two milliseconds prior to a current zero with relation to a 50 cycle-per-second frequency.

Another object of the present invention is the provision of an improved simplified-type and highly eflicient synchronous control for a circuit interrupter of the type in which separable contacts are biased to the open-circuit position, and are latched in the closed-circuit position, a holding magnet being utilized for effecting release of the latching means.

In United States patent application Serial Number 246,231 filed December 20, 1962, by Fritz Kesselring, Ernst Gisiger and Lutz Seguin, entitled Synchronous- Type Circuit Interrupter, and assigned to the assignee of the instant application, there is disclosed and claimed a novel type of synchronous-type circuit interrupter in which separable arcing contacts are biased toward the open circuit position, and are latched closed with an improved holding magnet being employed for controlling the release of the latching means as a function of the instantaneous value of the main current through the interrupter.

It is an additional object of the present invention to improve upon the holding magnet arrangement of the aforesaid patent application rendering it more simple and reliable over a wide range of main current values.

In accordance with the aforesaid patent application, there was provided a control system including a holding magnet, in which the magnetic flux of the holding magnet was composed of two flux components, which, in turn, were produced by two magnet systems, which were excited from the main current, and which'had a phase shift with respect to the main current of 90 and of substantially 0. It is a further object of the present invention to provide an improved holding magnet structure in which the characteristics of the two magnet systems, associated with the holding magnet, are determined with respect to each other in such manner that the time of the passage of zero flux condition in the holding magnet does not shift signifiv cantly even when the magnet systems are saturated.

It is an additional object of the present invention to provide an improved holding magnet construction for a synchronous-type circuit interrupter in which the holding magnet is arranged inside of a field-free metallic housing, which conducts the main current.

As set forth in the aforesaid patent application, there have been already proposed for synchronous-type circuit breakers control systems having a holding magnet in which the flux of the holding magnet is composed of two component fluxes, one of which is produced by a current which is approximately in phase with the rate-of-time changing of the flux in a magnet system having an air gap and being excited from the main current, hereinafter being called a current-transformer magnet system. The other component of the flux is produced by a magnet system which is magnetically coupled with the holding magnet, and which is excited from the main current passing through the interrupter, hereinafter being called a current magnet system.

A control system of this type may be so arranged that the armature of the holding magnet may, over a large range of values of the main current, be released at a predetermined time before the main current passes through its zero current value, whereupon the opening of the synchronous circuit interrupter is brought about. Experiments have shown, however, that systems of this type work reliably only as long as the current transformer magnet system and the current magnet system are essentially unsaturated, and the main current does not attain too high current values, for example, as long as the main current remains under 20,000 amperes.

If such a control system, as mentioned above, is to be used, in addition, for large current intensities, say up to 100,000 amperes, and more, for the control of synchronous-type circuit interrupters without undue difficulties, then the current-transformer magnet system and the current magnet system must have large air gaps and, therefore, large amounts of iron must be utilized in order that no undesirable saturation phenomena occurs. HOW- ever, in the case of such high current values, very strong magnetic fields occur in the vicinity of the conductors of the main current, which undesirably affect the holding magnet action in effecting release of the circuit interrupter. Such disadvantages which, of course, are noticeable only at high currents, are avoided by an application of the control system according to the present invention. More specifically, it is desirable to have the magnetization characteristics of both magnet systems excited from the main current, compensated for each other in such a manner that the passage through zero of the resulting flux in the holding magnet does not shift more than approximately /5 of a half cycle of the main current over the entire interrupting range of the breaker, including such current values of the main current which lead to saturation of the magnet systems. In addition, it is a very important feature of the present invention to arrange the holding magnet inside of a metallic housing which conducts the main current to obtain thereby a field-free ambient about the holding magnet.

It is, accordingly, a further object of the present invention to provide an improved synchronous-type circuit inparent upon reading the following specification taken in conjunction with the drawings, in which:

FIGURE 1 is a somewhat schematic view of the synchronous-type circuit interrupter embodying the principles of the present invention with the contact structure being illustrated in the closed-circuit position;

FIG. 2 is a sectional view taken through the current magnet system substantially along the line IIII of FIG. 1;

FIG. 3 graphically illustrates curves of the fluxes in both magnet systems; and,

FIG. 4 graphically illustrates experimentally-recorded tripping characteristics. With reference to FIG. 1, the reference numeral 1 designates the stationary contact cooperable with a movable contact 2 to establish an arc, effect the extinction thereof, and inerrupt the controlled circuit. As shown, the movable contact 2 is attached to an operating rod 3. The reference numeral 4 indicates a sliding contact arrangement suitable for conductivelycarrying the main current fromthe movable contact 2 through a conductive guide portion 5 of a metallic housing 6. In other words, the conductive tubular extension 5 represents the current inlet terminal for the metallic housing 6, and the reference numeral 7 designates the rod-shaped outlet current terminal therefor. Preferably, the metallic housing 6 is made of a good conducting material such as coppenaluminum, brass, etc.

Associated with the synchronous-typev circuit interrupter of FIG. 1 is a synchronous control SC comprising a first, or current-transformer magnet system 8 having at through the contact structure 1, 2, the metallic housing 6,

and through the axially extending rod-shaped portion 7.

It will be noted that the portion 9 of the current magnetic system, excited from the main current, is arranged exteriorly of the metallic housing 6, and is magnetically coupled with a holding magnet, generally designated by the reference numeral 12, by way of pole pieces 10 and 11. The reference numeral 13 indicates the armature of the holding magnet 12, which is securely attached to a latch 14, pivotally mounted on a stationary pivot 14a, and biased in a clockwise direction to a releasing position by means of a compression spring 15. The reference numeral 16 indicates the main latch, which locks the operating rod 3 of the circuit interrupter against the opening pressure exerted by a compression spring 17, which is compressed in the closed-circuit position of the interrupter, illustrated in-FIG. 1.

As shown, the accelerating opening compression spring 17 seats upon an interior portion 6a of the metallic housing 6 and also against an abutment 3a affixed by a transversely-extending pin 3b .to the operating rod 3.

A movable insulating operating rod 18 is secured to the armature 13 of the holding magnet 12. As will be explained more fully hereinafter, under normal operating conditions means are provided for preventing release of the holding armature 13; and for initiating asynchronous or synchronous operation, suitable means are provided to effect-movement of the insulating operating rod 18.

It will be apparent that the current-transformer magnet system 8 energizes the holding magnet 12 by a current 'i through a secondary conductor 19. The ohmic resistthe holding magnet 12, and, therefore acts as a magnetic cage, or shield, the inner space of which is substantially field-free. Experiments have shown that there exists no measurable effect upon the holding magnet 12 even at current values of 100,000 amperes.

But even when direct effect of the magnetic field of the current I on the holding magnet 12 is prevented in the above-described manner, nevertheless there still remains an undesirable shifting of the time instant at which the armature 13 releases as a result of saturation phenomena, to which the current-transformer magnet system 8 as well as the current magnet system 9 are exposed. The results of these saturation phenomena are explained more fully with reference to FIG. 3 of the drawings.

With reference to FIG. 3 of the drawings, I designates, as before, the current to be interrupted by the synchronous circuit interrupter. By means of the current-transformer magnet system 8 there is produced a current i which is phase-shifted by approximately with relation to the main current I. This current i develops in the iron circuit of the holding magnet 12 an out-of-phase component flux. With unsaturated conditions of the transformer 8, the wave shape of this flux component has the configuration designated by 5 Further, another flux component is produced in the holding magnet 12 by means of the magnetically-coupled current magnetic system 9, which flux component has, in the unsaturated condition of the current magnet system, the wave shape The armature 13 will be released from the holding magnet 12 as soon as the sum of these component fluxes and g5; in the holding magnet 12 are zero. As illustrated in FIG. 3, this point is t Let us assume now that at a larger main current value the current magnet system 9 is still unsaturated, but nevertheless the current-transformer magnet system 8 has reached the saturation point. The component flux produced in the holding magnet 12 by the current i has the wave shape qb Then the component fluxes and p become equal in magnitude in opposite directions only at the instant t which corresponds to an undesirablereductionof the advance release time. On the other hand,

if the current magnet system 9 saturates at a larger current first (flux wave shape while the current-transformer magnet system 8 still remains in an unsaturated condition, and accordingly produces the component flux 5 then the armature 13 of the holding magnet Will be released at the moment t i.e., closer to the maximum value of the main current.

This disadvantageous change in the position of the time instant for release of the armature 13 can he reduced in a simple manner to a tolerable degree by arranging the magnetization characteristics of both magnetic systems 8, 9 to compensate for each other, so that the effect of the saturation phenomena from the opposite sides of the advance release time approximately cancel each other out. For example, the magnetization characteristics of both systems 8, 9 can be balanced, so that according to FIG. 3 the current-transformer magnet system 8 produces by the current i the component flux in the holding magnet 12, and the magnetically-coupled current magnet system 9 produces the component magnetic flux p As it can be seen from FIG. 3, both magnetic flux components can be approximately canceled out from opposite sides in the desired time instant t Such results'can be obtained by determining the air gaps and the cross-sectional areas of both magnet systems 8, 9 in such manner as to properly arrive at such results experimentally. Especially, it has appeared advantageous to arrange an air gap in the form of an insulating plate 20 between the portion 9 and the pole pieces 10 and 1 1. That this problem can be solved is readily apparent from an inspection of FIG. 4, in which there is reproduced characteristics of advanced release times for a current range from 3,000 amperes up to 80,- 000 amperes taken on an experimental synchronous-type circuit breaker. The upper limit of the cross-hatched area holds for asymmetrical currents of a duration of 50 milliseconds, with respect to SO-cycles-per-second operametrical current waves having a half-wave time of 10 milliseconds on a 50-cycleper-second frequency basis.

The time Al is tabulated from the instant at which the armature 13 of the holding magnet 12 is released, and with it the latch 14 pulled back sufiiciently that the main latch 16 is released with. corresponding opening of the breaker, 'up to the passage through the zero value of the main. current I. It amounts to substantially /3 of the actual half-wave duration time. Its being dependent upon the current value of the main current is to be attributed to the residual shifting of the time instant at which the armature 13 releases. The shifting is, however, as seen from FIG- 4, in the entire tripping range less than /5 of the actual half-wave time. The arcing time is due to the contact engagement even shorter than At by approximately one millisecond. Also, it amounts at a low current to 3 or 2 milliseconds; at a higher current it amounts to only approximately one millisecond, so that an unobjectionable synchronous control is guaranteed over the entire current range.

Various means maybe provided to elfect closing of the interrupter. As shown in FIG. 1, a spring-biased pivotally-mounted operating lever 22 is provided, being pivoted adjacent a portion 6b of the metallic housing 6. The external end 22a of the rotatable closing lever 22 is pivotally connected, as at 23, to an armature 24 movable by the energization of a solenoid 25 by the closing of a closing button 26. An energizing source 27 may be provided in any convenient manner.

It will, therefore, be apparent that in the open circuit position of the movable contact structure 2 the lower end thereof will engage the operating roller 29, and may be closed by an energization of the solenoid 25. In the closed position, as is obvious, the main latch 16 will relatch the movable contact 2 with the accelerating compression spring 17 being compressed.

For effecting the opening operation, either a protective relay 31, responsive to the main line current, or an opening button 31a, for manual operation, may be employed. An energizing solenoid 33 effects downward opening movement of an armature 34 against the tension exerted by a biasing spring 35. The armature 34 is afiixed to an operating rod 37, the lower end of which is pivotally connected, as at 38, to a bell-crank 39, pivotally mounted, as at 40, to a fixed support 41.

The upper extremity of the arm 39a has a pin-and-slot connection 43 with respect to a rod end 44 afiixed to the extremity of the insulating operating rod 18.

From the foregoing construction, it will be apparent that normally the tension spring retains the armature 13 in engagement with the holding magnet 12. For asynchronous operation, with a relatively low load current passing through the interrupter, the opening button 31 may be pressed to energize the solenoid 33 and effect downward movement of the armature 34. The rotative opening movement of the bell-crank 39 will take up the lost motion in the pin-and-slot connection 43, and the flux exerted by the holding magnet 12 will be insufficient to retain the armature 13 in position. The release of the closing force exerted by spring 35 upon the armature 13 will enable the compression spring 15 to effect release of the holding armature 13 for asynchronous opening operation.

However, during the occurrence of relatively large currents, for example, approximately twice the nominal, or load current, and particularly during the occurrence of short-circuit currents, the synchronous control SC will at this time come into play in the previously described manner and retain the armature 13 in its closed latching position until the main current I descends toward its current zero value. Then, at the point t the release of the armature 13 will be effected in the previously described manner, and synchronous opening operation will take place.

Fromv the foregoing description it will be apparent that there is provided an improved synchronous control SC for a synchronous-type circuit interrupter in which the prerelease time At does not vary throughout wide tripping current values, as illustrated in FIG. 4 of the drawings. The addition of the metallic housing 6 to provide a fieldfree condition about the holding magnet 12 insures that at high current values extraneous magnet fields do not cause variance of the pre-release time.

Although there has been illustrated anddescribed a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

We claim as our invention:

1. A synchronous-type circuit interrupter including a pair of separable contacts for interrupting a main current, means biasing said pair of separable contacts to the opencircuit position, latching means for maintaining said contacts in engaged position against the bias exerted by said biasing means, releasing means to effect release of said latching means including a holding magnet, flux-producing means for said holding magnet including first and second magnetic systems for producing two component fluxes, said first and second magnetic systems being excited from said main current, said first magnetic system having an air gap and producing an induced, flux-generating current for the holding magnet which is approximately out of phase with the exciting main current, said second magnetic system excited from the main current being magnetically coupled with the holding magnet, and the magnetization characteristics of both magnetic systems being balanced for each other in such manner that the time of substantially zero flux in the holding magnet does not vary more than approximately one-fifth of a half cycle of the main current over the entire tripping range of the interrupter including those values of the main current which lead to saturation of the magnet systems.

2. A synchronous-type circuit interrupter including a pair of separable contacts for interrupting a main current, means defining a metallic housing for conducting the main current, means biasing said pair of separable contacts to the open-circuit position, latching means for maintaining said contacts in engaged position against the bias exerted by said biasing means, releasing means to eflect release of said latching means including a holding magnet, fluxproducing means for said holding magnet including first and second magnetic systems for producing two component fluxes, said first and second magnetic systems being excited from said main current, said first magnetic system having an air gap and producing an induced, fluxgenerating current for the holding magnet which is approximately 90 out of phase with the exciting main current, said second magnetic system excited from the main current being magnetically coupled with the holding magnet, the magnetization characteristics of both magnetic systems being balanced for each other in such manner that the time of substantially zero flux in the holding magnet does not vary more than approximately one-fifth of a half cycle of the main current over the entire tripping range of the interrupter including those values of the main current which lead to saturation of the magnet systems, and the holding magnet being positioned interiorly of said metallic housing for obtaining a field-free condition for the holding magnet, whereby large values of the main current will not influence the tripping value of the holding magnet.

3. A synchronous-type circuit interrupter including a pair of separable contacts for interrupting a main current means defining a metallic housing for conducting the main current, means biasing said pair of separable contacts to the open-circuit position, latching means for maintaining said contacts in engaged position against the bias exerted by said biasing means, releasing means to effect release of said latching means including a holding magnet, fiuxproducing means for said holding magnet including first and second magnetic systems for producing two compo'nent fluxes, said first and second magneticsystems be: ing' excited from said main current, said first magnetic system having an 'air' gap and producing an induced, fluxgenerating current for the holding magnet which is approximately 90" out of phase with the exciting main current, said second magnetic system excited from the main current being magnetically coupled with the holding magnet, the magnetization characteristics of both magnetic systems being balanced for each other in such manner that the time of substantially zero flux in the holding magnet does not vary'rnore than approximately one-fifth of a half-cycle of the main currentover the entire tripping range to the interrupter including those values of the main current which-lead to saturation of themagnet systems; the flux-producing part of said secondmagnetic' system being located exteriorly of said metallic housing, and the holding magnet being positioned interiorly of said metallic housing for obtaining a field-free condition for the holding.magnet, whereby large values of the main current will not influencethe tripping value of the holding magnet;

-No references cited;

BERNARD A1 GlLHEANY, Primary Examine r". ROBERT K. SCHAEFER, Examiner. 

1. A SYNCHRONOUS-TYPE CIRCUIT INTERRUPTER INCLUDING A PAIR OF SEPARABLE CONTACTS FOR INTERRUPTER A MAIN CURRENT, MEANS BIASING SAID PAIR OF SEPARBLE CONTACTS TO THE OPENCIRCUIT POSITION, LATCHING MEANS FOR MAINTAINING SAID CONTACTS IN ENGAGED POSITION AGAINST THE BIAS EXERTED BY SAID BIASING MEANS, RELEASING MEANS TO EFFECT RELEASE OF SAID LATCHING MEANS INCLUDING A HOLDING MAGNET, FLUX-PRODUCING MEANS FOR SAID HOLDING MAGNET INCLUDING FIRST AND SECOND MAGNETIC SYSTEMS FOR PRODUCTING TWO COMPONENT FLUXES, SAID FIRST AND SECOND MAGNETIC SYSTEMS BEING EXCITED FROM SAID MAINT CURRENT, SIAD FIRST MAGNETIC SYSTEM HAVING AN AIR GAP AND PRODUCING AN INDUCRED, FLUX-GENERATING CURRENT FOR THE HOLDING MAGNET WHICH IS APPROXIMATELY 90* OUT OF PHASE WITH THE EXCITING MAIN CURRENT, SAID SECOND MAG- 